Damage will nonetheless be substantial from Irma’s winds and floods, coming just a week after the hit taken by Houston from Hurricane Harvey, analysts said.

“Hurricane Irma’s last-minute shift westward was a bullet dodged from making this disaster so much worse than it is currently,” Duncan Ellis, Marsh L.L.C.’s U.S. property practice leader, said in an email. “We have seen some significant wind damage, however, as is often the case with these types of events. The surface rainwater combined with storm surge will be a major loss driver here, perhaps even greater than the wind damage.”

In a presentation at a Willis Re press conference at the Rendez-Vous de Septembre in Monte Carlo, Monaco, John Cavanagh, global CEO of Willis Re, Willis Towers Watson P.L.C. reinsurance intermediary unit, said Irma’s “point of landfall (was) favorable from (its) expected track two days ago.”

Analysts and observers see Irma, together with Harvey, as earnings events unlikely to eat into insurers’ capital. The storms may, however, cause some insurers to re-evaluate their perspectives on risk.

“The recent U.S. hurricanes are more likely to be earnings events than capital events,” according to reinsurance industry experts in a report published Monday by S&P Global Ratings Inc. called "Reinsurance Ratings Roundtable Panelists Comment on Impact of Hurricanes Harvey and Irma.”

“They nevertheless have the potential to change risk perceptions and management behavior,” S&P said in its report.

“These events will remind people that randomness is out there in the market. Even for the long periods when no hurricane made landfall, there was a level of randomness,” David Flandro, head of global analytics for JLT Re, a unit of Jardine Lloyd Thompson Group P.L.C., said in the report. He also agreed that the storms are more likely to be earnings events than capital events for the industry.

Catastrophe modeler AIR Worldwide on Monday estimated that U.S. insured losses resulting from Irma will range from $20 billion to $40 billion.

AIR’s estimates are based on the National Hurricane Center’s 5 p.m. EDT Sunday forecast advisory for Irma, the Boston-based unit of Verisk Analytics Inc. said in a statement.

Exposure value in the Florida coastal counties along the Gulf of Mexico up to Tampa, which will bear the brunt of the impact, is estimated at $1 trillion, according to AIR.

On Saturday, AIR said that combined insured losses for Irma for the United States and selected islands in the Caribbean will be between $20 billion and $65 billion, and the company had issued a somewhat broader range for the United States of $15 billion to $50 billion from Irma’s wind and storm surge.

On Sunday, Newark, California-based catastrophe modeler Risk Management Solutions Inc. said in a blog post by senior product manager Tom Sabbatelli that its modeling indicates there is a 10% chance of insured wind losses from Irma exceeding $60 billion.

Willis Re’s Mr. Cavanagh said post-event modeling for Harvey suggests actual wind loss will be less than $2 billion and that flood will be a much larger component, with key contributors to flood loss emerging from the auto, commercial and cargo/inland marine areas.

Insurers and exposures

The insurers most exposed to Florida commercial multiperil losses, according to data from Oldwick, New Jersey-based rating agency A.M. Best Co. Inc., are American International Group Inc., with $250.2 million of direct premiums written; Zurich North America, with $127.9 million; Heritage Insurance Group Inc. with $119.2 million; Nationwide Group with $83.2 million; and units of Chubb Ltd. with $78.6 million.

In its Weekly Cat Report issued Friday, Aon Benfield’s Impact Forecasting unit noted that population and housing growth in Florida have put more people and property at risk. Since the year 2000, the population has grown by more than 4 million people across central and southern sections of the state, the report said.

“Across the entire state of Florida, more than 2 million new homes have developed since 2000,” the Aon report said. “The majority of the growth has occurred in areas across the peninsula — raising the potential exposure at risk to natural disasters.”

Irvine, California-based CoreLogic Inc. said in an update Friday that about 8.5 million residential and commercial properties in Florida are at either extreme, very high or high risk of wind damage from Irma, while the firm’s storm surge analysis shows that about 3.5 million residential and commercial properties in Florida are at risk of hurricane-driven storm surge damage. Neither analysis includes potential damage from inland flooding, the statement said.

As with other major catastrophes, Irma will likely give rise to coverage questions and definitions

“Nearly every major catastrophe brings questions around coverage in a property policy and Irma will be no different,” Mr. Ellis said in the email. “In this case, the issue will likely be around the definition of ‘named windstorm’ versus ‘flood’ and where ‘storm surge’ and ‘surface water’ fall within those definitions. No two policies are alike. To avoid surprises and protracted disputes, organizations are encouraged to clearly understand how their property policies will respond to a natural catastrophe before one occurs.”